Prior to discussing the above chart, it is now irrefutable that modern global warming has disappeared over the last 15 years. This has been fully recognized by all climate alarmist scientists as they very publicly debate the reasons as to why their AGW models and predictions failed.

The plot above (Fig. A) represents the long-term temperature changes, with the monthly levels of atmospheric CO2 for context. Specifically, the temperature plot is the 30-year change in temperatures for each month since 1880. For example, the leftmost datapoint is the temperature change from January 1850 to January 1880 (360 months). For each month after January 1880, the 30-year change is plotted.

As the 30-year change plot indicates, there have been extended periods of both warming and cooling, regardless of the CO2 (ppm) levels. There are two distinct warming periods: the first starting March 1908 and ending December 1939; the second starting January 1974 and ending February 1998. Note the flattening and then downturn of 30-year temperature change after 1998, some 15 years ago.

The red curve represents the 5-year average of the long-term changes, leaving no doubt that the prior warming increase was just as "unprecedented" as the claimed modern warming after the mid-1970's.

What's the true climate reality? As is clearly depicted, the 5-year average shows no impact from the continuous, monotonous rise of CO2 levels after 1950. And modern global warming is not accelerating, nor unequivocal - in fact, the modern warming is pretty much like past warming periods.

In more detail (click to enlarge) the two similar warming periods are plotted in the above two charts. Figure B on the left is for the period stretching a total of 382 months, with a long-term temperature linear trend of 2.4°C per century. Over this extended time period, CO2 levels only increased by 12 ppm from a very low point, reflecting relatively small human CO2 emissions prior to the modern consumer/industrial society.

Figure C represents the modern "unprecedented" and "catastrophic" long-term global warming as claimed by the climate alarmists. In reality, this modern warming lasted only 290 months and produced a global warming trend some 0.6 degrees less than the earlier period before collapsing after 1998. This "dangerous" warming occurred during a period of much higher atmospheric CO2 levels that quickly increased by 36 ppm (3 times more growth than early 20th century warming period).

Conclusions: The global warming science facts are unequivocal that long-term temperature change is not being significantly driven by higher human CO2 emissions, but ore likely a result of natural internal/external factors (ENSO, cosmic/solar, etc.). Climate reality is that the earlier 20th century warming (1908-1939) was more intense, producing a higher linear trend for long-term temperature change, and lasting considerably longer than the modern warming period (1974-1998). The stronger warming during the earlier 20th century took place despite CO2 levels being significantly below the alarmist's supposed "safe" CO2 levels of 350 ppm; and, the CO2 level increases during that period were one-third those of the modern warming.